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Abstract:

A current fuse includes: a fuse portion that is disposed on a substrate;
and a conductive portion that is placed in an overlying layer above the
fuse portion or an underlying layer between the substrate and the fuse
portion, has the same potential as that of one portion of the fuse
portion when a current is passed through the fuse portion, and extends
apart from the fuse portion from the one portion side of the fuse portion
as far as an overlying layer above or an underlying layer below another
portion of the fuse portion whose potential differs from that of the one
portion.

Claims:

1. A current fuse comprising: a fuse portion that is disposed on a
substrate; and a conductive portion that is placed in an overlying layer
above the fuse portion or an underlying layer between the substrate and
the fuse portion, has the same potential as that of one portion of the
fuse portion when a current is passed through the fuse portion, and
extends apart from the fuse portion from the one portion side of the fuse
portion as far as an overlying layer above or an underlying layer below
another portion of the fuse portion whose potential differs from that of
the one portion.

2. The current fuse according to claim 1, further comprising a connecting
portion that extends from the one portion of the fuse portion to the
overlying layer or the underlying layer and electrically interconnects
the one portion of the fuse portion and the conductive portion.

3. The current fuse according to claim 1, wherein the other portion of
the fuse portion has a higher potential than that of the one portion of
the fuse portion.

4. The current fuse according to claim 3, wherein the fuse portion has a
first terminal portion on a ground side, a second terminal portion on an
applying side, and a fuse element connected to both of the terminal
portions, the connecting portion is connected to the first terminal
portion, and the conductive portion extends from the first terminal
portion side as far as an overlying layer above or an underlying layer
below an intermediate section of the fuse element.

5. The current fuse according to claim 4, wherein the conductive portion
extends as far as the overlying layer above or the underlying layer below
a midsection of the fuse element.

6. The current fuse according to claim 2, wherein the fuse portion has a
first terminal portion on a ground side, a second terminal portion on an
applying side, and a fuse element connected to both of the terminal
portions, the connecting portion has a first connecting portion connected
to the first terminal portion and a second connecting portion connected
to the second terminal portion, and the conductive portion has a first
conductive portion that is electrically connected to the fuse portion via
the first connecting portion and extends from the first terminal portion
side as far as an overlying layer above or an underlying layer below an
intermediate section of the fuse element and a second conductive portion
that is electrically connected to the fuse portion via the second
connecting portion, extends from the second terminal portion side toward
the first terminal portion side, and is apart from and opposes the first
conductive portion.

7. A current fuse comprising: a fuse portion that is disposed on a
substrate and is configured to include a first terminal portion on a
ground side, a second terminal portion on an applying side, and a fuse
element connected to both of the terminal portions; and a conductive
portion that is placed in an overlying layer above the fuse portion or an
underlying layer between the substrate and the fuse portion, is
electrically connected to the first terminal portion, and extends apart
from the fuse portion from the first terminal portion side as far as an
overlying layer above or an underlying layer below an intermediate
section of the fuse element.

8. The current fuse according to claim 4, wherein the width of the fuse
element is narrower than the widths of both of the terminal portions.

9. The current fuse according to claim 7, wherein the width of the fuse
element is narrower than the widths of both of the terminal portions.

10. The current fuse according to claim 4, wherein the width of the
conductive portion is longer than the width of the fuse element.

11. The current fuse according to claim 7, wherein the width of the
conductive portion is longer than the width of the fuse element.

12. The current fuse according to claim 4, wherein the fuse element has
two first fuse elements that are connected to respectively different
places of the second terminal portion serving as the applying side and
extend from the second terminal portion toward the first terminal
portion, a joint portion at which the two first fuse elements join
together, and a second fuse element that extends from the joint portion
to the first terminal portion, and the conductive portion electrically
connected to the first terminal portion extends as far as an overlying
layer above or an underlying layer below an intermediate section of the
second fuse element.

13. The current fuse according to claim 7, wherein the fuse element has
two first fuse elements that are connected to respectively different
places of the second terminal portion serving as the applying side and
extend from the second terminal portion toward the first terminal
portion, a joint portion at which the two first fuse elements join
together, and a second fuse element that extends from the joint portion
to the first terminal portion, and the conductive portion electrically
connected to the first terminal portion extends as far as an overlying
layer above or an underlying layer below an intermediate section of the
second fuse element.

14. The current fuse according to claim 2, wherein an interlayer
insulating layer is disposed between the fuse portion and the conductive
portion, the connecting portion comprises a conductor buried inside a
hole penetrating the interlayer insulating layer, and the conductive
portion is placed in an underlying layer below the fuse portion.

15. The current fuse according to claim 7, an interlayer insulating layer
is disposed between the fuse portion and the conductive portion, a
connecting portion between the conductive portion and the first terminal
portion comprises a conductor buried inside a hole penetrating the
interlayer insulating layer, and the conductive portion is placed in an
underlying layer below the fuse portion.

16. A semiconductor device comprising: a semiconductor substrate; an
insulating layer that is formed on the semiconductor substrate; and the
current fuse according to claim 1 which is formed on the insulating
layer.

17. A semiconductor device comprising: a semiconductor substrate; an
insulating layer that is formed on the semiconductor substrate; and the
current fuse according to claim 7 which is formed on the insulating
layer.

18. A method of blowing a current fuse where a fuse portion is disposed
on a substrate, the method comprising placing a conductive portion having
a single potential apart from the fuse portion in an overlying layer
above the fuse portion or an underlying layer between the substrate and
the fuse portion and utilizing the conductive portion to concentrate an
electric field in one portion of the fuse portion and melt the fuse
portion.

19. The method of blowing a current fuse according to claim 18, wherein
the fuse portion has a first terminal portion on a ground side, a second
terminal portion on an applying side, and a fuse element connected to
both of the terminal portions, and as the conductive portion, the method
uses a first conductive portion that is electrically connected to the
fuse portion via a first connecting portion connected to the first
terminal portion and extends from the first terminal portion side as far
as an overlying layer above or an underlying layer below an intermediate
section of the fuse element and a second conductive portion that is
electrically connected to the fuse portion via a second connecting
portion connected to the second terminal portion, extends from the second
terminal portion side toward the first terminal portion side, and is
apart from and opposes the first conductive portion.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based on and claims priority under 35 USC 119
from Japanese Patent Application No. 2010-081346 filed on Mar. 31, 2010,
the disclosure of which is incorporated by reference herein.

BACKGROUND

[0002] 1. Technical Field

[0003] The present invention relates to a current fuse, a semiconductor
device, and a method of blowing a current fuse.

[0004] 2. Related Art

[0005] As a conventional current fuse, there is known a current fuse
equipped with a fuse portion including a single-layer conductor on the
surface of an insulating substrate as described, for example, in Japanese
Patent Application Laid-Open (JP-A) No. 2003-151425 and JP-A No.
2003-173728.

[0006] FIG. 10A is a diagram showing a top view of a current fuse equipped
with the same conventional configuration as in JP-A No. 2003-151425. A
conventional current fuse 500 is equipped with a fuse portion 502 such as
described above on an unillustrated insulating substrate. This fuse
portion 502 has a fuse element 504 that melts when an overcurrent flows
through it.

[0007] The fuse element 504 has a slender rectangular shape when seen in a
top view, and a first joint portion 506 is connected to one lengthwise
direction end portion thereof. The first joint portion 506 is connected
to a first terminal portion 510 electrically connected to a ground 508
and joins together the fuse element 504 and the first terminal portion
510. Further, a second joint portion 512 is connected to the other
lengthwise direction end portion of the fuse element 504. The second
joint portion 512 is connected to a second terminal portion 516
electrically connected to an applying portion 514 that applies a 10 V
voltage, for example, and the second joint portion 512 joins together the
fuse element 504 and the second terminal portion 516.

[0008] In this current fuse 500, when a current is passed through the fuse
portion 502, as shown in FIG. 10B, the equipotential lines in the fuse
element 504 are formed at equal intervals and the electric field is made
uniform.

[0009] However, in this conventional configuration, it has been necessary
to perform optimization of the optimum blow voltage (current) in order to
prevent (the fuse element 504 of) the fuse portion 502 from not blowing
in a case where an overcurrent flows through the fuse portion 502, so
extracting the conditions of that optimization has taken time.

SUMMARY

[0010] In view of the above-described circumstances, it is an object of
the present invention to provide a current fuse, a semiconductor device,
and a method of blowing a current fuse with which a fuse portion can be
easily blown.

[0011] A current fuse pertaining to a first aspect of the invention
includes: a fuse portion that is disposed on a substrate; and a
conductive portion that is placed in an overlying layer above the fuse
portion or an underlying layer between the substrate and the fuse
portion, has the same potential as that of one portion of the fuse
portion when a current is passed through the fuse portion, and extends
apart from the fuse portion from the one portion side of the fuse portion
as far as an overlying layer above or an underlying layer below another
portion of the fuse portion whose potential differs from that of the one
portion.

[0012] According to this configuration, the current fuse is equipped with
the conductive portion that has the same potential as that of one portion
of the fuse portion and extends apart from the fuse portion from the one
portion side of the fuse portion as far as the overlying layer above or
the underlying layer below the other portion of the fuse portion whose
potential differs from that of the one portion. For this reason, the
electric field concentrates in the other portion. As a result of this,
when an overcurrent flows through the fuse portion, the current density
becomes locally high and the Joule heat becomes higher at the other
portion where the electric field concentrates, and the fuse portion can
be easily blown (melted) at the other portion.

[0013] The phrase "the electric field concentrates" refers to the
equipotential lines concentrating and the electric field becoming
stronger.

[0014] A current fuse pertaining to a second aspect of the invention is
the current fuse pertaining to the first aspect, further including a
connecting portion that extends from the one portion of the fuse portion
to the overlying layer or the underlying layer and electrically
interconnects the one portion of the fuse portion and the conductive
portion.

[0015] In this way, because the one portion of the fuse portion and the
conductive portion are electrically interconnected via the connecting
portion, the conductive portion can be given the same potential as that
of the one portion of the fuse portion.

[0016] A current fuse pertaining to a third aspect of the invention is the
current fuse pertaining to the first aspect or the second aspect, wherein
the other portion of the fuse portion has a higher potential than that of
the one portion of the fuse portion.

[0017] According to this configuration, the conductive portion extends
from the one portion side of the fuse portion as far as the other portion
side whose potential is higher than that of the one portion.

[0018] A current fuse pertaining to a fourth aspect of the invention is
the current fuse pertaining to the third aspect, wherein the fuse portion
has a first terminal portion on a ground side, a second terminal portion
on an applying side, and a fuse element connected to both of the terminal
portions, the connecting portion is connected to the first terminal
portion, and the conductive portion extends from the first terminal
portion side as far as an overlying layer above or an underlying layer
below an intermediate section of the fuse element.

[0019] According to this configuration, the electric field from the second
terminal portion as far as the intermediate section of the fuse element
can be concentrated in the other portion of the fuse portion (the
intermediate section of the fuse element), and the fuse portion can be
more easily blown (melted) at the intermediate section.

[0020] A current fuse pertaining to a fifth aspect of the invention is the
current fuse pertaining to the fourth aspect, wherein the conductive
portion extends as far as the overlying layer above or the underlying
layer below a midsection of the fuse element.

[0021] According to this configuration, the electric field from the second
terminal portion side as far as the midsection of the fuse element can be
concentrated in the other portion of the fuse portion (the midsection of
the fuse element), and the fuse portion can be more easily blown (melted)
at the midsection.

[0022] A current fuse pertaining to a sixth aspect of the invention is the
current fuse pertaining to the second aspect, wherein the fuse portion
has a first terminal portion on a ground side, a second terminal portion
on an applying side, and a fuse element connected to both of the terminal
portions, the connecting portion has a first connecting portion connected
to the first terminal portion and a second connecting portion connected
to the second terminal portion, and the conductive portion has a first
conductive portion that is electrically connected to the fuse portion via
the first connecting portion and extends from the first terminal portion
side as far as an overlying layer above or an underlying layer below an
intermediate section of the fuse element and a second conductive portion
that is electrically connected to the fuse portion via the second
connecting portion, extends from the second terminal portion side toward
the first terminal portion side, and is apart from and opposes the first
conductive portion.

[0023] According to this aspect, the electric field can be concentrated
more locally in the fuse element located in the underlying layer below or
the overlying layer above the place where the first conductive portion
and the second conductive portion are apart.

[0024] A current fuse pertaining to a seventh aspect of the invention
includes: a fuse portion that is disposed on a substrate and is
configured to include a first terminal portion on a ground side, a second
terminal portion on an applying side, and a fuse element connected to
both of the terminal portions; and a conductive portion that is placed in
an overlying layer above the fuse portion or an underlying layer between
the substrate and the fuse portion, is electrically connected to the
first terminal portion, and extends apart from the fuse portion from the
first terminal portion side as far as an overlying layer above or an
underlying layer below an intermediate section of the fuse element.

[0025] According to this configuration, the conductive portion that
extends from the first terminal portion side as far as the overlying
layer above or the underlying layer below the fuse element has the same
potential as the potential of the first terminal portion, and the
electric field concentrates in the intermediate section of the fuse
element. As a result of this, when an overcurrent flows through the fuse
portion, the current density becomes locally high and the Joule heat
becomes higher at the intermediate section of the fuse element where the
electric field concentrates, and the fuse portion can be easily blown
(melted) at the intermediate section of the fuse element.

[0026] A current fuse pertaining to an eighth aspect of the invention is
the current fuse pertaining to any one of the fifth to seventh aspects,
wherein the width of the fuse element is narrower than the widths of both
of the terminal portions.

[0027] According to this configuration, the electric field becomes
stronger in the fuse element and the fuse portion blows.

[0028] A current fuse pertaining to a ninth aspect of the invention is the
current fuse pertaining to any one of the fourth to eighth aspects,
wherein the width of the conductive portion is longer than the width of
the fuse element.

[0029] According to this configuration, the width of the conductive
portion is longer than the width of the fuse element, so it becomes
possible to realize more reliable blowing of the fuse portion because the
electric field concentrates in the entire transverse width of the fuse
element.

[0030] A current fuse pertaining to a tenth aspect of the invention is the
current fuse pertaining to any one of the fourth to ninth aspects,
wherein the fuse element has two first fuse elements that are connected
to respectively different places of the second terminal portion serving
as the applying side and extend from the second terminal portion toward
the first terminal portion, a joint portion at which the two first fuse
elements join together, and a second fuse element that extends from the
joint portion to the first terminal portion, and the conductive portion
electrically connected to the first terminal portion extends as far as an
overlying layer above or an underlying layer below an intermediate
section of the second fuse element.

[0031] According to this configuration, in a case where the same amount of
current flows through the two first fuse elements respectively connected
to different places of the second terminal portion, about twice the
current flows through the second fuse element from the joint portion to
the first terminal portion as compared to each of the first fuse
elements, and the electric field concentrates in the second fuse element
(the current density becomes larger). Further, because the conductive
portion extends as far as the overlying layer above or the underlying
layer below the intermediate section of the second fuse element, the
electric field further concentrates in the intermediate section of the
second fuse element through which about twice the current flows as
compared to each of the first fuse elements. Consequently, the fuse
portion can be more easily blown at the intermediate section of the
second fuse element.

[0032] A current fuse pertaining to an eleventh aspect of the invention is
the current fuse pertaining to any one of the second to tenth aspects,
wherein an interlayer insulating layer is disposed between the fuse
portion and the conductive portion, the connecting portion includes a
conductor buried inside a hole penetrating the interlayer insulating
layer, and the conductive portion is placed in an underlying layer below
the fuse portion.

[0033] According to this configuration, the conductive portion is placed
in the underlying layer below the fuse portion, whereby it becomes
possible to prevent a situation where, for example, an unillustrated open
portion is disposed above the fuse portion and, at the time when the fuse
portion blows, fragments and so forth of the blown fuse portion fly
inside a device to which the current fuse is attached.

[0034] Further, because the interlayer insulating layer is disposed
between the fuse portion and the conductive portion, the conductive
portion and the fuse portion no longer contact each other except for at
the connecting portion.

[0035] A semiconductor device pertaining to a twelfth aspect of the
invention includes: a semiconductor substrate; an insulating layer that
is formed on the semiconductor substrate; and the current fuse pertaining
to any one of the first to eleventh aspects of the invention which is
formed on the insulating layer.

[0036] In this way, the current fuse can also be applied to a
semiconductor device.

[0037] A method of blowing a current fuse pertaining to a thirteenth
aspect of the invention is a method of blowing a current fuse where a
fuse portion is disposed on a substrate, the method including placing a
conductive portion having a single potential apart from the fuse portion
in an overlying layer above the fuse portion or an underlying layer
between the substrate and the fuse portion and utilizing the conductive
portion to concentrate an electric field in one portion of the fuse
portion and melt the fuse portion.

[0038] According to this blowing method, by concentrating the electric
field in the one portion of the fuse portion, high Joule heat can be
generated in the one portion as compared to the other portion of the fuse
portion, and the one portion can be easily blown (melted).

[0039] A method of blowing a current fuse pertaining to a fourteenth
aspect of the invention is the method of blowing a current fuse
pertaining to the thirteenth aspect of the invention, wherein the fuse
portion has a first terminal portion on a ground side, a second terminal
portion on an applying side, and a fuse element connected to both of the
terminal portions, and as the conductive portion, the method uses a first
conductive portion that is electrically connected to the fuse portion via
a first connecting portion connected to the first terminal portion and
extends from the first terminal portion side as far as an overlying layer
above or an underlying layer below an intermediate section of the fuse
element and a second conductive portion that is electrically connected to
the fuse portion via a second connecting portion connected to the second
terminal portion, extends from the second terminal portion side toward
the first terminal portion side, and is apart from and opposes the first
conductive portion.

[0040] According to this blowing method, the electric field can be
concentrated more locally in the fuse element located in the underlying
layer below or the overlying layer above the place where the first
conductive portion and the second conductive portion are apart as
compared to the method blowing a current fuse pertaining to the
thirteenth aspect.

[0041] Because the present invention is given the configuration described
above, it can provide a current fuse, a semiconductor device, and a
method of blowing a current fuse with which a fuse portion can be easily
blown.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Exemplary embodiments of the present invention will be described in
detail based on the following figures, wherein:

[0043]FIG. 1 is a general top view showing the structure of a current
fuse pertaining to a first exemplary embodiment of the present invention;

[0053]FIG. 9 is a general top view showing the structure of a current
fuse pertaining to a third exemplary embodiment of the present invention;

[0054] FIG. 10A is an explanatory diagram regarding a method of blowing a
conventional current fuse and is a diagram showing a top view; and

[0055] FIG. 10B is a diagram showing a sectional view of the conventional
current fuse.

DETAILED DESCRIPTION

First Exemplary Embodiment

[0056] A current fuse, a semiconductor device, and a method of blowing a
current fuse pertaining to a first exemplary embodiment of the present
invention will be described below on the basis of the drawings. First,
the structure of the current fuse pertaining to the first exemplary
embodiment of the present invention will be described.

[0057] --Structure--

[0058]FIG. 1 is a general top view showing the structure of the current
fuse pertaining to the first exemplary embodiment of the present
invention, and FIG. 2 is a sectional view as seen from line A-A of FIG.
1.

[0059] As shown in FIG. 2, a current fuse 10 pertaining to the first
exemplary embodiment of the present invention is configured in such a way
that an insulating layer 14 including an insulator such as a BPSG (Boron
Phosphor Silicate Glass) film, for example, is formed on a semiconductor
substrate 12 such as a silicon wafer. A conductive portion 16 is formed
on this insulating layer 14.

[0060] The conductive portion 16 includes a conductor such as AlSiCu, for
example, and its upper surface is covered by an interlayer insulating
layer 18 similarly formed on the insulating layer 14. This interlayer
insulating layer 18 includes an insulator such as a NSG (Non-doped
Silicate Glass) film or a plasma oxide film, for example, and a fuse
portion 20 is formed on the interlayer insulating layer 18. This fuse
portion 20 includes a conductor such as AlSiCu like the conductive
portion 16, for example, and one end portion of the conductive portion 16
and one end portion of the fuse portion 20 are electrically
interconnected via a connecting portion 22. This connecting portion 20 is
a so-called through hole including a conductor such as copper or tungsten
buried inside a hole 24 penetrating the interlayer insulating layer 18.

[0061] A protective layer including an insulator such as a plasma nitride
film, for example, is disposed on the interlayer insulating layer 18 so
as to cover the area surrounding the fuse portion 20. The protective
layer is omitted throughout all the drawings. Further, in the present
invention, "upper" refers to the direction of the fuse portion 20 using
the semiconductor substrate 12 as a reference and "lower" refers to the
direction of the semiconductor substrate 12 using the fuse portion 20 as
a reference.

[0062] Next, the configurations of the fuse portion 20 and the conductive
portion 16 will be specifically described using FIG. 1. In FIG. 1, the
substrate 12 and the interlayer insulating layer 18 and so forth are
omitted.

[0063] The fuse portion 20 has a fuse element 30 that melts when an
overcurrent flows through it. This fuse element 30 has a slender
rectangular shape when seen in a top view. The length of the fuse element
30 in its lengthwise direction is 10 μm, for example, and the length
(width) of the fuse element 30 in its widthwise direction is 1.2 μm,
for example.

[0064] Additionally, a first joint portion 32 is connected to one
lengthwise direction end portion of the fuse element 30. Further, a
second joint portion 34 is connected to the other lengthwise direction
end portion of the fuse element 30. The first joint portion 32 and the
second joint portion 34 (called "both of the joint portions" below) have
trapezoidal shapes when seen in a top view and slant by 45 degrees toward
the fuse element 30 side such that their widths gradually become
narrower.

[0065] The first joint portion 32 is connected to a first terminal portion
38 electrically connected to a ground 36 and joins together the fuse
element 30 and the first terminal portion 38. Further, the second joint
portion 34 is connected to a second terminal portion 40 electrically
connected to an applying portion 42 that applies a 10 V voltage, for
example, and the second joint portion 34 joins together the fuse element
30 and the second terminal portion 40.

[0066] The widths of the first terminal portion 38 and the second terminal
portion 40 (called "both of the terminal portions" below) are 6 μm,
for example, and are wider than the width of the fuse element 30.

[0067] One end portion each of three, for example, of the connecting
portions 22 are arranged in the width direction an interval apart from
each other and contact the lower surface of the first terminal portion
38.

[0068] Each of the connecting portions 22 extends linearly downward from
the lower surface of the first terminal portion 38 of the fuse portion
20, and the other end portion of each of the connecting portions 22
contacts the upper surface of the aforementioned conductive portion 16.
The conductive portion 16 is placed in an underlying layer below the fuse
portion 20 with the interlayer insulating layer 18 being sandwiched
therebetween, has the same potential (about 0 V) as that of one portion
of the fuse portion 20 (the portion of the fuse portion 20 that contacts
the connecting portions 22) when a current is passed through the fuse
portion 20, and extends from the one portion side of the fuse portion 20
as far as an underlying layer below another portion of the fuse portion
20 whose potential differs from that of the one portion.

[0069] Specifically, in the first exemplary embodiment, the other portion
is an intermediate section of the fuse element 30--such as, for example,
a midsection of the fuse element 30--whose potential is higher than that
of the one portion of the fuse portion 20, and the conductive portion 16
extends linearly apart from the fuse portion 20 from the underlying layer
below the portion of the fuse portion 20 that contacts the connecting
portions 22 as far as the underlying layer below the midsection of the
fuse element 30.

[0070] Further, the width of the conductive portion 16 is longer than the
width of the fuse portion 20 and particularly the width of the fuse
element 30.

[0071] --Manufacturing Method--

[0072] Next, a method of manufacturing the current fuse pertaining to the
first exemplary embodiment of the present invention will be described.

[0073]FIG. 3A to FIG. 3J are diagrams showing the method of manufacturing
the current fuse pertaining to the first exemplary embodiment of the
present invention.

[0074] First, as shown in FIG. 3A, the insulating layer 14 including a
BPSG film or the like is formed by CVD or the like, for example, on the
semiconductor substrate 12 such as a Si wafer.

[0075] Next, as shown in FIG. 3B, a conductive film 16A including AlSiCu
or the like is formed by sputtering or the like, for example, on the
insulating layer 14. Then, as shown in FIG. 3C, a photoresist 50 is
applied or sprayed onto the surface of the conductive film 16A and is
patterned by a photolithographic process, and the conductive film 16A is
processed by a dry etching process to form the conductive portion 16.
After this conductive portion 16 has been formed, the photoresist 50 on
the conductive portion 16 is removed by a solvent or the like.

[0076] Next, as shown in FIG. 3D, the interlayer insulating layer 18
including a NSG film or the like, for example, is formed by CVD or the
like, for example, on the insulating layer 14 and the conductive portion
16. Thereafter, as shown in FIG. 3E, a photoresist 52 is applied or
sprayed onto the surface of the interlayer insulating layer 18 and is
patterned by a photolithographic process, and the interlayer insulating
layer 18 is processed by a dry etching process to form the hole 24. After
this hole 24 has been formed, the photoresist 52 on the interlayer
insulating layer 18 is removed by a solvent or the like.

[0077] Next, as shown in FIG. 3F, a conductive film 54 including copper or
tungsten or the like is formed by sputtering or the like, for example, on
the interlayer insulating layer 18, and some of the conductive film 54 is
buried in the hole 24. After this conductive film 54 has been formed, as
shown in FIG. 3G, the conductive film 54 except for the portion buried in
the hole 24 is removed by a dry etching process to form the connecting
portion 22 (through hole) in the hole 24.

[0078] Next, as shown in FIG. 3H, a conductive film 56 including AlSiCu or
the like is formed by sputtering or the like, for example, on the
interlayer insulating layer 18. Then, as shown in FIG. 3I, a photoresist
58 is applied or sprayed onto the surface of the conductive film 56 and
is patterned by a photolithographic process, and the conductive film 56
is processed by a dry etching process to form the fuse portion 20.

[0079] After the fuse portion 20 has been formed, as shown in FIG. 3J, the
photoresist 58 on the fuse portion 20 is removed by a solvent or the
like. Finally, an insulating film (not shown) including a plasma nitride
film or the like is formed by CVD or the like, for example, on the
interlayer insulating film 18 and the fuse portion 20, a protective film
(not shown) is formed by a photolithographic process and an etching
process, and the fuse portion 20 is exposed.

[0080] The current fuse 10 shown in FIG. 1 and FIG. 2 is completed through
the manufacturing process described above.

[0081] --Action (Method of Blowing Current Fuse)--

[0082] Next, the method of blowing the current fuse 10 pertaining to the
first exemplary embodiment of the present invention will be described.

[0083]FIG. 4A and FIG. 4B are explanatory diagrams regarding the method
of blowing the current fuse 10 pertaining to the first exemplary
embodiment of the present invention, with FIG. 4A being a top view of the
current fuse 10 pertaining to the first exemplary embodiment of the
present invention and FIG. 4B being a sectional view as seen from line
A-A of FIG. 4A. The lines showing voltages in the drawings are
equipotential lines. In FIG. 4A and FIG. 4B, the substrate 12 and the
interlayer insulating layer 18 and so forth are omitted.

[0084] First, in the current fuse 10 pertaining to the first exemplary
embodiment of the present invention, a current is passed through the fuse
portion 20. That is, the first terminal portion 38 is connected to the
ground 36, and the second terminal portion 40 is connected to the
applying portion 42. Then, a 10 V voltage is applied from the applying
portion 42 to the second terminal portion 40. When this happens, a
current flows through the fuse element 30 connected to the first terminal
portion 38 and the second terminal portion 40, an electric field is
generated, and the potential of the fuse element 30 becomes lower
continuously from the second terminal portion 40 side toward the first
terminal portion 38 side.

[0085] Here, in the conventional configuration, as shown in FIG. 10A and
FIG. 10B, the equipotential lines in the fuse element 504 are formed at
equal intervals and the electric field is made uniform. Consequently, the
same Joule heat has been generated in all portions of the fuse element
504.

[0086] However, in the configuration of the first exemplary embodiment of
the present invention, as shown in FIG. 4A and FIG. 4B, the conductive
portion 16 that extends apart from the fuse portion 20 as far as the
underlying layer below the midsection of the fuse element 30 is not
electrically connected to the fuse portion 20 except for at the
connecting portions 22, so the current does not flow through it, and the
conductive portion 16 has the same potential (about 0 V) as that of the
first terminal portion 38 to which it is electrically connected via the
connecting portions 22. As a result of this, the equipotential lines are
formed in avoidance of the conductive portion 16, and the electric field
concentrates in the midsection of the fuse element 30 (the section marked
by X in FIG. 4A). Additionally, with this configuration, when an
overcurrent flows through the fuse portion 20, the current density
becomes locally high and the Joule heat becomes higher at the midsection
of the fuse element 30 where the electric field concentrates, and the
fuse portion 20 can be easily blown (melted) at the midsection.

[0087] The phrase "the electric field concentrates" refers to the
equipotential lines concentrating and the electric field becoming
stronger.

[0088] Further, according to the configuration of the first exemplary
embodiment of the present invention, the conductive portion 16 extends
apart from the fuse portion 20 as far as the underlying layer below the
midsection of the fuse element 30. For this reason, the electric field
from the second terminal portion 40 side as far as the midsection of the
fuse element 30 can be concentrated in the midsection. Thus, the fuse
portion 20 can be more easily blown (melted) at the midsection.

[0089] Further, according to the configuration of the first exemplary
embodiment of the present invention, the width of the fuse element 30 is
narrower than the widths of both of the terminal portions 38 and 40. For
this reason, the electric field becomes stronger in the fuse element 30
and the fuse portion 20 blows.

[0090] Further, the width of the conductive portion 16 is longer than the
width of the fuse portion 20 and particularly the width of the fuse
element 30. For this reason, it becomes possible to realize more reliable
blowing of the fuse portion 20 because the electric field concentrates in
the entire transverse width of the fuse portion 20 and particularly the
fuse element 30.

[0091] Further, according to this configuration, the conductive portion 16
is placed is the underlying layer below the fuse portion 20, whereby it
becomes possible to prevent a situation where, for example, an
unillustrated open portion is disposed above the fuse portion 20 and, at
the time when the fuse portion 20 blows, fragments and so forth of the
blown fuse portion 20 fly inside a device to which the current fuse 10 is
attached.

[0092] Further, because the interlayer insulating layer 18 is disposed
between the fuse portion 20 and the conductive portion 16, the conductive
portion 16 and the fuse portion 20 reliably no longer contact each other
except for at the connecting portions 22.

[0093] Further, this current fuse 30 can also be effectively applied to a
semiconductor device because it is equipped with the semiconductor
substrate 12.

Second Exemplary Embodiment

[0094] Next, a current fuse, a semiconductor device, and a method of
blowing a current fuse pertaining to a second exemplary embodiment of the
present invention will be described on the basis of the drawings. First,
the structure of the current fuse pertaining to the second exemplary
embodiment of the present invention will be described.

[0095] --Structure--

[0096]FIG. 5 is a general top view showing the structure of the current
fuse pertaining to the second exemplary embodiment of the present
invention, and FIG. 6 is a sectional view as seen from line B-B of FIG.
5.

[0097] As shown in FIG. 6, a current fuse 100 pertaining to the second
exemplary embodiment of the present invention is configured in such a way
that an insulating layer 104 including an insulator such as a BPSG (Boron
Phosphor Silicate Glass) film, for example, is formed on a semiconductor
substrate 102 such as a silicon wafer. Two conductive portions including
a first conductive portion 106 and a second conductive portion 107 that
are apart from and oppose each other in the same layer are formed on this
insulating layer 104.

[0098] The conductive portions 106 and 107 includes a conductor such as
AlSiCu, for example, and their upper surfaces are covered by an
interlayer insulating layer 108 similarly formed on the insulating layer
104. This interlayer insulating layer 108 includes a NSG (Non-doped
Silicate Glass) film or a plasma oxide film or the like, for example, and
a fuse portion 110 is formed on the interlayer insulating layer 108.

[0099] This fuse portion 110 includes a conductor such as AlSiCu like both
of the conductive portions 106 and 107, for example, and one end portion
of the first conductive portion 106 and one end portion of the fuse
portion 110 are electrically interconnected via a first connecting
portion 112. Further, one end portion of the second conductive portion
107 and the other end portion of the fuse portion 110 are electrically
interconnected via a second connecting portion 113. Both of the
connecting portions 112 and 113 are so-called through holes including a
conductor such as copper or tungsten buried inside holes 114 and 115
penetrating the interlayer insulating layer 108.

[0100] A protective layer including an insulator such as a plasma nitride
film, for example, is disposed on the interlayer insulating layer 108 so
as to cover the area surrounding the fuse portion 110, but the protective
layer is omitted throughout all the drawings.

[0101] Next, the configurations of the fuse portion 110 and the conductive
portions 106 and 107 will be specifically described using FIG. 5. In FIG.
5, the substrate 102 and the interlayer insulating layer 108 and so forth
are omitted.

[0102] The fuse portion 110 has a fuse element 130 that melts when an
overcurrent flows through it. This fuse element 130 has a slender
rectangular shape when seen in a top view. The length of the fuse element
130 in its lengthwise direction is 10 μm, for example, and the length
(width) of the fuse element 130 in its widthwise direction is 1.2 μm,
for example.

[0103] Additionally, a first joint portion 132 is connected to one
lengthwise direction end portion of the fuse element 130. Further, a
second joint portion 134 is connected to the other lengthwise direction
end portion of the fuse element 130. The first joint portion 132 and the
second joint portion 134 (called "both of the joint portions" below) have
trapezoidal shapes when seen in a top view and slant by 45 degrees toward
the fuse element 130 side such that their widths gradually become
narrower.

[0104] The first joint portion 132 is connected to a first terminal
portion 138 electrically connected to a ground 136 and joins together the
fuse element 130 and the first terminal portion 138. Further, the second
joint portion 134 is connected to a second terminal portion 140
electrically connected to an applying portion 142 that applies a 10 V
voltage, for example, and the second joint portion 134 joins together the
fuse element 130 and the second terminal portion 140.

[0105] The widths of the first terminal portion 138 and the second
terminal portion 140 (called "both of the terminal portions" below) are 6
μm, for example, and are wider than the width of the fuse element 130.

[0106] One end portion each of three, for example, of the first connecting
portions 112 are arranged in the width direction an interval apart from
each other and contact the lower surface of the first terminal portion
138.

[0107] Each of the first connecting portions 112 extends linearly downward
from the lower surface of the first terminal portion 138 of the fuse
portion 110, and the other end portion of each of the first connecting
portions 112 contacts the upper surface of the aforementioned first
conductive portion 106. The first conductive portion 106 is placed in an
underlying layer below the fuse portion 110 with the interlayer
insulating layer 108 being sandwiched therebetween, has the same
potential (about 0 V) as that of one portion of the fuse portion 110 (the
portion of the fuse portion 110 that contacts the first connecting
portions 112) when a current is passed through the fuse portion 110, and
extends from the one portion side of the fuse portion 110 as far as an
underlying layer below another portion of the fuse portion 110 whose
potential differs from that of the one portion.

[0108] Specifically, in the second exemplary embodiment, the other portion
is the fore of an intermediate section of the fuse element 130--such as,
for example, a midsection of the fuse element 130--whose potential is
higher than that of the one portion of the fuse portion 110, and the
first conductive portion 106 extends apart from the fuse portion 110
linearly from the underlying layer below the portion of the fuse portion
110 that contacts the first connecting portions 112 as far as the
underlying layer below the fore of the midsection of the fuse element
130.

[0109] One end portion each of three, for example, of the second
connecting portions 113 are arranged in the width direction an interval
apart from each other and contact the lower surface of the second
terminal portion 140.

[0110] Each of the second connecting portions 113 extends linearly
downward from the lower surface of the second terminal portion 140 of the
fuse portion 110, and the other end portion of each of the second
connecting portions 113 contacts the upper surface of the aforementioned
second conductive portion 107. The second conductive portion 107 is
placed in an underlying layer below the fuse portion 110 with the
interlayer insulating layer 108 being sandwiched therebetween and has the
same potential (about 10 V) as that of the portion of the second terminal
portion 140 that contacts the second connecting portions 112.

[0111] Further, the second conductive portion 107 extends apart from the
fuse portion 110 linearly from the second terminal portion 140 side
toward the first terminal portion side 138, and is apart from and opposes
the first conductive portion 106 in the underlying layer below the
midsection of the fuse element 130.

[0112] --Manufacturing Method--

[0113] Next, a method of manufacturing the current fuse pertaining to the
second exemplary embodiment of the present invention will be described.

[0114]FIG. 7A to FIG. 7J are diagrams showing the method of manufacturing
the current fuse pertaining to the second exemplary embodiment of the
present invention.

[0115] First, as shown in FIG. 7A, the insulating layer 104 including a
BPSG film or the like is formed by CVD or the like, for example, on the
semiconductor substrate 102 such as a Si wafer.

[0116] Next, as shown in FIG. 7B, a conductive film 105 including AlSiCu
or the like is formed by sputtering or the like, for example, on the
insulating layer 104. Then, as shown in FIG. 7C, a photoresist 150 is
applied or sprayed onto the surface of the conductive film 105 and is
patterned by a photolithographic process, and the conductive film 105 is
processed by a dry etching process to form the first conductive portion
106 and the second conductive portion 107. After both of the conductive
portions 106 and 107 have been formed, the photoresist 150 on both of the
conductive portions 106 and 107 is removed by a solvent or the like.

[0117] Next, as shown in FIG. 7D, the interlayer insulating layer 108
including a NSG film or the like, for example, is formed by CVD or the
like, for example, on the insulating layer 104 and both of the conductive
portions 106 and 107. Thereafter, as shown in FIG. 7E, a photoresist 152
is applied or sprayed onto the surface of the interlayer insulating layer
108 and is patterned by a photolithographic process, and the interlayer
insulating layer 108 is processed by a dry etching process to form the
holes 114 and 115. After these holes 114 and 115 have been formed, the
photoresist 152 on the interlayer insulating layer 108 is removed by a
solvent or the like.

[0118] Next, as shown in FIG. 7F, a conductive film 154 including copper
or tungsten or the like is formed by sputtering or the like, for example,
on the interlayer insulating layer 108, and some of the conductive film
154 is buried in the holes 114 and 115. After this conductive film 154
has been formed, as shown in FIG. 7G the conductive film 154 except for
the portions buried in the holes 114 and 115 is removed by a dry etching
process to form the first connecting portion 112 and the second
connecting portion 113 (through holes) in the holes 114 and 115.

[0119] Next, as shown in FIG. 7H, a conductive film 156 including AlSiCu
or the like is formed by sputtering or the like, for example, on the
interlayer insulating layer 108. Then, as shown in FIG. 7I, a photoresist
158 is applied or sprayed onto the surface of the conductive film 156 and
is patterned by a photolithographic process, and the conductive film 156
is processed by a dry etching process to form the fuse portion 110.

[0120] After the fuse portion 110 has been formed, as shown in FIG. 7J,
the photoresist 158 on the fuse portion 110 is removed by a solvent or
the like. Finally, an insulating film (not shown) including a plasma
nitride film or the like is formed by CVD or the like, for example, on
the interlayer insulating film 108 and the fuse portion 110, a protective
film (not shown) is formed by a photolithographic process and an etching
process, and the fuse portion 110 is exposed.

[0121] The current fuse 100 shown in FIG. 5 and FIG. 6 is completed
through the manufacturing process described above.

[0122] --Action (Method of Blowing Current Fuse)--

[0123] Next, the method of blowing the current fuse 100 pertaining to the
second exemplary embodiment of the present invention will be described.

[0124]FIG. 8A and FIG. 8B are explanatory diagrams regarding the method
of blowing the current fuse 100 pertaining to the second exemplary
embodiment of the present invention, with FIG. 8A being a top view of the
current fuse 100 pertaining to the second exemplary embodiment of the
present invention and FIG. 8B being a sectional view as seen from line
B-B of FIG. 8A. The lines showing voltages in the drawings are
equipotential lines. In FIG. 8A and FIG. 8B, the substrate 102 and the
interlayer insulating layer 108 and so forth are omitted.

[0125] First, in the current fuse 100 pertaining to the second exemplary
embodiment of the present invention, a current is passed through the fuse
portion 110. That is, the first terminal portion 138 is connected to the
ground 136, and the second terminal portion 140 is connected to the
applying portion 142. Then, a 10 V voltage is applied from the applying
portion 142 to the second terminal portion 140. When this happens, a
current flows through the fuse element 130 connected to the first
terminal portion 138 and the second terminal portion 140, an electric
field is generated, and the potential of the fuse element 130 becomes
lower continuously from the second terminal portion 140 side toward the
first terminal portion 138 side.

[0126] Here, in the configuration of the second exemplary embodiment of
the present invention, as shown in FIG. 8A and FIG. 8B, the first
conductive portion 106 that extends apart from the fuse portion 110 as
far as the underlying layer below the fore of the midsection of the fuse
element 130 is not electrically connected to the fuse portion 110 except
for at the first connecting portions 112. For this reason, the current
does not flow through it, and the first conductive portion 106 has the
same potential (about 0 V) as that of the first terminal portion 138 to
which it is electrically connected via the first connecting portions 112.
Similarly, the second conductive portion 107 that opposes the first
conductive portion 106 an interval apart from the first conductive
portion 106 is not electrically connected to the fuse portion 110 except
for at the second connecting portions 113. For this reason, the current
does not flow through it, and the second conductive portion 107 has the
same potential (about 10 V) as that of the second terminal portion 140 to
which it is electrically connected via the second connecting portions
113.

[0127] As a result of this, the equipotential lines are formed in
avoidance of the first conductive portion 106 and the second conductive
portion 107. Thus, the electric field concentrates in the fuse element
130 located in the overlying layer above the gap formed between the first
conductive portion 106 and the second conductive portion 107--that is, in
the midsection (the section marked by X in FIG. 8A) of the fuse element
130. Additionally, with this configuration, when an overcurrent flows
through the fuse portion 110, the current density becomes locally high
and the Joule heat becomes higher at the midsection of the fuse element
130 where the electric field concentrates, and the fuse portion 110 can
be easily blown (melted) at the midsection.

[0128] Additionally, in the configuration of the second exemplary
embodiment, as compared to the first exemplary embodiment, the second
conductive portion 107 is disposed, whereby it becomes possible to blow
the fuse portion 110 reliably because the electric field can be
concentrated more locally in the fuse element 130.

Third Exemplary Embodiment

[0129] Next, a current fuse, a semiconductor device, and a method of
blowing a current fuse pertaining to a third exemplary embodiment of the
present invention will be described on the basis of the drawings.

[0130] --Structure--

[0131]FIG. 9 is a general top view showing the structure of the current
fuse pertaining to the third exemplary embodiment of the present
invention. In FIG. 9, the substrate and the interlayer insulating layer
and so forth are omitted.

[0132] A current fuse 200 pertaining to the third exemplary embodiment of
the present invention is equipped with a fuse portion 201 on an
unillustrated semiconductor substrate. Like in the first exemplary
embodiment, this fuse portion 201 has a first terminal portion 204
connected to a ground 202 and a second terminal portion 208 connected to
an applying portion 206. However, in the third exemplary embodiment, the
configuration of the fuse element connected to the first terminal portion
204 and the second terminal portion 208 differs from that in the first
exemplary embodiment.

[0133] That is, in the third exemplary embodiment, the fuse element
connected to the first terminal portion 204 and the second terminal
portion 208 has two first fuse elements 210 that are connected to
respectively different places of the second terminal portion 208 and
extend from the second terminal portion 208 toward the first terminal
portion 204, a joint portion 212 at which the two first fuse elements 210
join together, and a second fuse element 214 that extends from the joint
portion 212 to the first terminal portion 204.

[0134] Further, one end portion each of three, for example, connecting
portions 216 are arranged in the width direction an interval apart from
each other and contact the lower surface of the first terminal portion
104.

[0135] Each of the connecting portions 216 extends linearly downward from
the lower surface of the first terminal portion 204 of the fuse portion
201, and the other end portion of each of the connecting portions 216
contacts the upper surface of a conductive portion 218. The conductive
portion 208 is placed in an underlying layer below the fuse portion 201
with the unillustrated interlayer insulating layer being sandwiched
therebetween, has the same potential (about 0 V) as that of one portion
of the fuse portion 201 (the portion of the fuse portion 201 that
contacts the connecting portions 216) when a current is passed through
the fuse portion 201, and extends from the one portion side of the fuse
portion 201 as far as an underlying layer below another portion of the
fuse portion 201 whose potential differs from that of the one portion.

[0136] Specifically, in the third exemplary embodiment, the other portion
is an intermediate section of the second fuse element 214--such as, for
example, the section of the fuse element just before the joint portion
212--whose potential is higher than that of the one portion of the fuse
portion 201, and the conductive portion 218 extends apart from the fuse
portion 201 linearly from the underlying layer below the portion of the
fuse portion 201 that contacts the connecting portions 216 as far as the
underlying layer just before the second fuse element 214.

[0137] --Action (Method of Blowing Current Fuse)--

[0138] As described above, according to the configuration of the current
fuse pertaining to the third exemplary embodiment of the present
invention, in a case where the same amount of current flows through the
two first fuse elements 210 connected to different places of the second
terminal portion 208, about twice the current flows through the second
fuse element 214 from the joint portion 212 to the first terminal portion
204 as compared to each of the first fuse elements 210, and the electric
field concentrates in the second fuse element 214 (the current density
becomes larger). Further, because the conductive portion 218 extends
apart from the fuse portion 201 as far as the underlying layer just
before the joint portion 212 of the second fuse element 214, the electric
field further concentrates in the section just before the joint portion
212 of the second fuse element 214 through which about twice the current
flows as compared to each of the first fuse elements 210. Consequently,
the fuse portion 201 can be more easily blown at the section just before
the joint portion 212 of the second fuse element 214.

[0139] (Modifications)

[0140] The present invention is not limited to the exemplary embodiments
described above and is capable of various modifications, changes, and
improvements.

[0141] For example, in the exemplary embodiments described above, cases
where the current fuses 10, 100, and 200 are formed on the semiconductor
substrates 12 and 102 have been described. However, these may also be
formed on a glass substrate, a plastic substrate, a ceramic substrate, a
polyimide substrate, etc. Further, the shape of the substrate is also not
particularly limited, and it suffices for the substrate to be a so-called
substrate serving as a foundation on which the fuse is formed.

[0142] Further, cases where a protective film is disposed have been
described, but the present invention can also be applied to a current
fuse in which a protective film is not disposed.

[0143] Further, the current fuses 10, 100, and 200 described above can be
applied to a semiconductor device.

[0144] Further, cases where the conductive portion 16, the first
conductive portion 106, the second conductive portion 107, and the
conductive portion 218 are disposed in an underlying layer below the fuse
portions 20, 110, and 201 have been described, but the conductive
portions may also be disposed in an overlying layer above the fuse
portions 20, 110, and 201. However, it is preferable to dispose the
conductive portion in an underlying layer below the fuse portion so that
it is possible to prevent, at the time when the fuse portions 20, 110,
and 210 blow, fragments and so forth of the blown fuse portions 20, 110,
and 210 from flying inside devices to which the current fuses 10, 100,
and 200 are attached.

[0145] Further, in the third exemplary embodiment, the current fuse may
also have a configuration that does not have the conductive portion 218.
That is, in a case where the same amount of current flows through the two
first fuse elements 210 connected to different places of the second
terminal portion 208, about twice the current flows through the second
fuse element 214 from the joint portion 212 to the first terminal portion
204 as compared to each of the first fuse elements 210, and the electric
field concentrates in the second fuse element 214 (the current density
becomes larger), so the fuse portion 201 can be more easily blown even
with just the configuration of the fuse portion 201.

[0146] Further, in the first exemplary embodiment, a case where the
conductive portion 16 is electrically connected to the fuse portion 20
via the connecting portions 22 has been described, but the current fuse
may also have a configuration where, for example, the conductive portion
16 is connected to the ground 36 and is not connected to the fuse portion
20. In this case, the connecting portions 22 are unnecessary. Moreover,
the connecting portions 22 may also be connected to the fuse portion 20
other than at the first terminal portion 38. Consequently, they may also
be connected to the second terminal portion 40 or the fuse element 30. In
a case where the connecting portions 22 are connected to the second
terminal portion 40, the conductive portion 16 extends from the second
terminal portion 40 side toward the first terminal portion 38 side.

[0147] Further, a case where the width of the fuse element 30 is narrower
than the widths of both of the terminal portions 38 and 40 has been
described, but the width of the fuse element 30 does not have to be
narrower than the widths of both terminal portions 38 and 40. However, it
is preferable for the width of the fuse element 30 to be narrower than
the widths of both of the terminal portions 38 and 40.